Fetal and neonatal exposure to AZT and low-protein diet affects glucose homeostasis: a model with implications for AIDS prevention

Acute nutritional stress during pregnancy affects placental efficiency, fetal growth and adult glucose homeostasis

Exposure to maternal malnutrition impairs postnatal health. Acute nutritional stress is less clearly implicated in intrauterine programming. We studied the effects of stressing pregnant mothers on perinatal growth and adult glucose homeostasis. We compared one group ("stressed", mothers fasted for 16 hours) with controls ("unstressed"). We found that fasting stress had adverse effects on the weight of the fetuses conceived (p<0.005) and the placental efficiency (p<0.001) in stressed compared to unstressed offspring. Placental weight was increased (p<0.001) presumably in compensation. Stress affected the glucose homeostasis of the offspring when they became adults (p<0.005) when analysed as individuals. We previously linked nutritional stress throughout pregnancy with a mitochondrial stress response. We modelled placenta with cultured human trophoblast cells (BeWos) and fetal tissues with mouse embryonic fibroblasts (MEFs). High throughput imaging showed that the mitochondria of both cell types underwent a similar sequence of changes in morphology, induced by nutritional stresses. The contrasting stress responses on fetal and placental weight were not captured by the cellular models. The stress of maternal fasting may be an important determinant of perinatal outcome in the mouse and might be relevant to nutritional stress in human pregnancy.

Prenatal exposure to tobacco smoke leads to increased mitochondrial DNA content in umbilical cord serum associated to reduced gestational age

We investigated if prenatal exposures to tobacco smoke lead to changes in mitochondrial DNA content (mtDNA) in cord serum and adversely affect newborns' health. Umbilical cord serum cotinine levels were used to determine in utero exposure to smoking. Cord serum mtDNA was measured by quantitative polymerase chain reaction analysis of the genes coding for cytochrome c oxidase1 (MT-CO1) and cytochrome c oxidase2 (MT-CO2). Log transformed levels of mtDNA coding for MT-CO1 and MT-CO2 were significantly higher among infants of active smokers with higher serum level of cotinine (p < 0.05) and inversely associated with gestational age (p = 0.08; p = 0.02). Structural equation modeling results confirmed a positive association between cotinine and MT-CO1 and2 (p < 0.01) and inverse associations with gestational age (p = 0.02) and IGF-1 (p < 0.01). We identified a dose-dependent increase in the level of MT-CO1 and MT-CO2 associated to increased cord serum cotinine and decreased gestational age.

Is Placental Mitochondrial Function a Regulator that Matches Fetal and Placental Growth to Maternal Nutrient Intake in the Mouse?

Background

Effective fetal growth requires adequate maternal nutrition coupled to active transport of nutrients across the placenta, which, in turn requires ATP. Epidemiological and experimental evidence has shown that impaired maternal nutrition in utero results in an adverse postnatal phenotype for the offspring. Placental mitochondrial function might link maternal food intake to fetal growth since impaired placental ATP production, in response to poor maternal nutrition, could be a pathway linking maternal food intake to reduced fetal growth.

Method

We assessed the effects of maternal diet on placental water content, ATP levels and mitochondrial DNA (mtDNA) content in mice at embryonic (E) day 18 (E18). Females maintained on either low- (LPD) or normal- (NPD) protein diets were mated with NPD males.

Results

To investigate the possibility of an underlying mitochondrial stress response, we studied cultured human trophoblast cells (BeWos). High throughput imaging showed that amino acid starvation induces changes in mitochondrial morphology that suggest stress-induced mitochondrial hyperfusion. This is a defensive response, believed to increase mitochondrial efficiency, that could underlie the increase in ATP observed in placenta.

Conclusions

These findings reinforce the pathophysiological links between maternal diet and conceptus mitochondria, potentially contributing to metabolic programming. The quiet embryo hypothesis proposes that pre-implantation embryo survival is best served by a relatively low level of metabolism. This may extend to post-implantation trophoblast responses to nutrition.

Gestational protein restriction in mice has pronounced effects on gene expression in newborn offspring's liver and skeletal muscle; protective effect of taurine

We examined gene expression changes in liver and skeletal muscle of newborn mice subjected to a maternal low protein (LP) or normal protein (NP) diet during pregnancy, with or without taurine supplementation in the drinking water. LP offspring had a 40% lower birthweight than NP offspring, whereas it was reduced by only 20% with taurine supplementation. Microarray gene expression analysis revealed significant changes in 2012 genes in liver and 967 genes in skeletal muscle of LP offspring. By unknown mechanisms, taurine partially or fully prevented 30 and 46% of these expression changes, respectively. Mitochondrial genes, in particular genes associated with oxidative phosphorylation, were more abundantly changed in LP offspring, with primarily up-regulation in liver but down-regulation in skeletal muscle. In both tissues, citrate synthase activity remained unchanged. Taurine preferentially rescued changes in genes concerned with fatty acid metabolism in liver and with oxidative phoshorylation and tri carboxylic acid (TCA) cycle in skeletal muscle.

ABBREVIATIONS

Gestational protein restriction resulted in lower birthweight associated with significant gene expression changes, which was different in liver and muscle of offspring. However, a major part of the birthweight decrease and the expression changes were prevented by maternal taurine supplementation, implying taurine is a key component in metabolic fetal programming.

Mitochondria and diabetes mellitus: untangling a conflictive relationship?

Diabetes mellitus is occasionally observed in patients with skeletal muscle respiratory chain deficiency, suggesting that skeletal muscle mitochondrial dysfunction might play a pathogenic role in type 2 diabetes (T2D). In support of this hypothesis, decreased muscle mitochondrial activity has been reported in T2D patients and in mouse models of diabetes. However, recent work by several groups suggests that decreased muscle mitochondrial function may be a consequence rather than a cause of diabetes, since decreased mitochondrial function in mice affords protection from diabetes and obesity. We review the data on this controversial but important issue of potential links between mitochondrial dysfunction and diabetes.

A common mitchondrial DNA variant is associated with thinness in mothers and their 20-yr-old offspring

A common mitochondrial (mt)DNA variant that is maternally inherited, the 16189 variant, is associated with type 2 diabetes and thinness at birth. To elucidate the association of the variant with thinness, we studied the 16189 variant in a well-characterized Australian cohort (n = 161) who were followed up from birth to age 20 yr. PCR analysis and mtDNA haplotyping was carried out on DNA from 161 offspring from consecutive, normal, singleton pregnancies followed from birth to age 20 yr. The 16189 mtDNA variant was present in 14 of the 161 20 yr olds (8.7%). Both the mothers with the 16189 variant and their 20-yr-old offspring were thinner than those without. Median (interquartile range) BMI was 21.9 kg/m(2) (20.4 to 22.9) in mothers with the variant compared with 23.5 (21.4 to 26.6) in those without (P = 0.013) and 22.2 (21.1 to 23.8) in 20 yr olds with the variant compared with 22.7 (20.8 to 25.6) in those without (P = 0.019). The 16189 variant was also associated with a high placental weight and high placental-to-birth weight ratio (P = 0.051 and P = 0.0024, respectively). Insulin sensitivity was normal in 20 yr olds with the 16189 variant. This contrasts with 20 yr olds who did not have the variant but who had been thin or small at birth and who had normal BMI and normal placental-to-birth weight ratio, but were insulin resistant. This study suggests that the 16189 mtDNA variant is associated with maternally inherited thinness in young adults. This may be mediated by effects on mtDNA replication and, thence, placental function. Further research is required to confirm these hypotheses.